I have a 2008 Mustang GT. Decently sized disc brakes, not the best, but adequate for the performance level of the car.
Anyhow, its been my observational experience that front brakes work much harder than the rear brakes (which is why front rotors/calipers are often much larger than the rear brakes, as is the case on my car) due to weight transfer when braking, the weight of the engine being in the front (in most cars), etc.
This also manifests itself in the accumulation of brake dust. I am in the car wash business and I see so many front wheels that are filthy while the rear wheels are practically brake-dust free. BMW’s and Volvo’s seem particularly notorious for mass amounts of brake dust generation (why is that anyway?) on the front wheels.
Which leads to my question. I have been noticing that when I clean my car, which is often, wiping down the rear wheels results in more brake dust than the fronts.
Last time I got my car serviced, in which they do a multi-point inspection, they listed the rear brakes as having 7 (out of 12) millimeters of life while the fronts had 8mm.
Why is this? Why would my rear brakes, being smaller and in the lighter rear end of the car be wearing faster than the fronts?